Combustion control



AU8- 2,5 1942 J. J. KLINKr-:R 2,293,830

coMBUsT'IoN CONTROL F5941 i. i

2 sheets-sheet 2 Filed Aug. 24. 1959 JOHN J. KLINKER Patented Aug. 25,1942 unirse COMBUSTION CONTROL John J. Klinker, Decatur, Ill., assignorto A. W. Cash Company, Decatur, Ill., a corporation of DelawareApplication August 24, 1939, Serial No. 291,687

3 Claims.

This invention relates to combustion control, and more particularly tothe control of combustion in furnaces having a fuel bed through whichair is caused to flow solely by maintenance of a sub-atmosphericpressure at the furnace outlet. This sub-atmospheric pressure may beproduced either by a stack (natural draft), or by a fan or itsequivalent (induced draft),

In furnaces of this type the rate of combustion is determined by therate of air flow through the fuel bed, but this air flow is dependentupon several variables, including the draft available and the thicknessand character of the fuel bed. Thus it is dificult to maintain anydesired constant rate of combustion. The problem is even more serious ininstallations having a plurality of furnaces among which the load isdivided, for if the fuel bed on one furnace becomes thin this furnacewill operate at a higher combustion rate than the others, and the fuelbed will tend to become even thinner, accentuating the unbalancedconditions. Variations in the distribution of the draft among therespective furnaces will cause similar difficulties.

It is accordingly one object of the invention to provide a simple andinexpensive apparatus for controlling combustion in furnaces of theaforesaid type and for maintaining the rate of combustion at a desiredvalue.

It is a further object of the invention to prof vide a simple andinexpensive apparatus for controlling combustion and ensuring a desireddistribution of the load among a plurality of furnaces of the aforesaidtype,

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specication and covered by the claims appended hereto.

Referring to the drawings illustrating one embodiment of the invention,and in which like reference numerals indi-cate like parts:

Fig. 1 is a front elevation of a pair of steam boiler furnaces andassociated combustion control apparatus, certain parts being broken awayfor clearness of illustration; and

Fig. 2 is a view similar to Fig. 1 showing a modified form of theinvention.

The embodiment illustrated in Fig. 1 comprises a pair of furnaces I0 setin battery and each having a grate H to which fuel may be suppliedmanually through the usual fire-doors l2. Associated with each furnaceis a steam boiler I4, both boilers delivering steam to a main header I5.Each furnace is provided with the usual gas outlet duct or uptake I6having a damper i8 therein, both uptakes being connected to a breechingi9 leading to a stack or other draftinducing means (not shown). Beneatheach grate is a chamber 20 from which the air for combustion passesupwardly through the grate and the fuel bed. Air is admitted directlyfrom the atmosphere into each chamber 29 through a restricted inletopening 22 in the front wall thereof. Each chamber 2l) is locatedimmediately anterior to the fuel bed, in which the initial combustion ofthe fuel takes place.

Ea-ch of the dampers i8 is regulated iny such a manner as to maintain apredetermined pressure in the corresponding chamber 2l) beneath the fuelbed, and to vary this pressure in accordance with changes in the demandfor heat. The pressure in each chamber 2l) is of course always somewhatbelow atmospheric, since the air flow is slightly restricted in passingthrough the openings 22. Each damper is provided with a shaft 23 havingan arm 24 thereon which is connected by a link 26 to the fluid-actuatedmotor 21 of a regulator 28 of the general type disclosed in the patentto Temple No. 1,992,048. This regulator comprises a pilot valvemechanism 30 connected to the motor 2l by two pipes 3l and supplied withfluid under pressure from a suitable source through a pipe 32. The pilotvalve mechanism is controlled by a lever 34 actuated by a flexiblediaphragm 35 which is loaded by a coiled tension spring 355. Theregulator 28 is connected to the coresponding space 2l) beneath thegrate Il by means of a pipe 33. This pipe is preferably provided with arestriction in the form of a valve 39, and with a restricted air inletopening in the form of a branch pipe having a valve 4 I, these partsbeing so arranged that the diaphragm 35 is subjected to the pressurebetween the valves 39 and di. This pressure is of course a function ofthe pressure in the space 20.

The loading of the diaphragm 35 in both the regulators 28 is varied inaccordance with the demand for heat. For this purpose there is provideda suitable regulator 43 responsive to variations in the steam pressurein the header l5, this pressure being transmitted to the regulatorthrough a pipe M. This regulator may be of any suitable type, onesatisfactory construction being shown in the patent to Temple No.2,049,549. The regulator 4S is connected by a link 45 to an arm M on ahorizontal shaft i8 rotatably supported in suitable bearings 49. Thisshaft carries two arms 5I, each of which is connected by a link 52 to alever 53 on one of the regulators 28. Each lever 53 is connected to avertically slidable screw 55 carrying a nut 56 to which the upper end ofthe corresponding spring 36 is secured. With this construction, theregulator 48 will respond to any variation in the steam pressure in theheader I5, and by rotating the shaft 48 it will cause the screws 55 tomove up or down as the case may be, thus changing the loading forcesapplied by the springs 35 to the diaphragme 35.

The operation of this embodiment of the invention will now be apparentfrom the a-bove disclosure. With a bed of fuel burning on each of thegrates II, the air for combustion will enter the chambers 20 through theopenings 22 and pass upwardly through the fuel. The gaseous products ofcombustion will give up most of their heat to the boilers I4 and thenescape through the uptakes I5 to the breeching I9. The steam generatedin the boilers will pass into the header I5 and thence to a place ofuse, There will be a continuous flow of a small stream of air inwardlythrough each valve 4I, pipe 38, and valve 39 to the corresponding space20, and so long as the pressure in the space 29 remains constant thepressure effective on the diaphragm 35 will remain constant, and theuptake damper I8 will remain stationary. If however the pressure in thespace should vary in the slightest degree for any reason, such aschanges in the thickness or character of the fuel bed, changes in thedraft loss through the boiler caused by soot accumulations, or changesin the ydraft available at the uptake IG, the diaphragm 35 will move andby actuating the pilot valve mechanism 36 it will cause the motor 21 toadjust the uptake damper I8 until the desired pressure is restored inthe space 20. If the demand for steam should increase slightly, thesteam pressure in the header I5 will decrease, and the regulator '33will act through its mechanical connection with the screws 55 to raisethese screws, increasing the tension of the springs 36 and throwing theregulators 28 out of balance. Consequently the motors 21 will open thedampers I8 until the pressure in the spaces 2! has ybeen loweredsufficiently to restore the regulators 28 to a balanced condition.Similarly a decrease in the demand for steam will result in an increasein the steam pressure, and a closing movement of the uptake dampers I8.In this manner a predetermined relationship will be maintained betweenthe demand for steam and the rate of fiow of the combustion air asdetermined by the pressure differential across each inlet opening 22.Furthermore, the load will be equally divided between the two boilers,irrespective of differences in the fuel beds or other variable factors.By adjusting one or both of the valves 39 and 5I, it is possible tochange the operating range of the regulator 28 and thus adapt thecontrol system to the particular conditions encountered at eachinstallation.

In Fig. 2 there is shown a modified form of the invention in which asomewhat different arrangement of the regulating apparatus is disclosed.Since the construction of the furnaces and boilers is the same as inFig. 1, the same reference numerals have been utilized so far as theyare applicable. In Fig. 2 the regulators 28 of Fig. l have been replaced'by regulators 28a in which the nuts 55 that support the springs 35 aremounted on manually adjustable screws 58, these screws being xed in theaxial direction. Furthermore each regulator 28a is provided with anadditional diaphragm 59 which is connected to the main diaphragm 35 andforms a means whereby the loading of the main dia- Dhragm may beautomatically varied. The pressure in each chamber 2O is transmitted tothe corresponding regulator 28a through a pipe 60. Means is provided toapply a fluid pressure to the diaphragms 59 of both the regulators 28a,and to vary this fluid pressure in accordance with variations in thedemand for heat, as indicated for example by changes in the steampressure in the header I5. For this purpose I have shown a pilotcontroller 6I connected to the header I5 by a pipe 62 and supplied witha suitable pressure fluid, such as compressed air, through a pipe 63. Apipe 54 leads from the controller to the diaphragm chamber 66 of apressure reducing and regulating valve 61. The pilot controller BI maybe of any suitable and well-known construction adapted to reduce thepressure of the air supplied by the pipe 63 and to transmit the reducedpressure through the pipe G5, the amount of pressure reduction beingvaried in accordance with variations in the steam pressure transmittedto the controller through the pipe 62. The valve 61 is also ofwell-known construction and comprises a diaphragm 69 arranged to actuatea reciprocable valve member II which controls the flow of a suitablefluid, such as compressed air, from a supply pipe 13 to a delivery pipe14. The diaphragm 69 is urged upwardly against the pressure in thechamber 65 by means of a spring 'I5 and by the fluid pressure at thedelivery side of the valve member II. The delivery pipe 'I4 is connectedto the regulators 28u by means of branch pipes TI which supply pressureto the loading diaphragms 59. Each branch pipe is provided with arestriction 78 and with a manually adjustable leak-off valve 79 leadingto the atmosphere.

The operation of this embodiment of the invention will now be apparentfrom the above disclosure. The air for combustion will enter thechambers 20 through the openings 22 and pass upwardly through the fuelon the grates I I. The combustion gases will give up most of their heatto the boilers IB, which will generate steam and deliver the samethrough the header I5 to a place of use. So long as the steam pressureremains constant at the desired value, the controller 6I will transmit aconstant pressure through the pipe 64 to the diaphragm 69, and the valvemember II will be held slightly open against the force of the spring 'I0and the pressure in the delivery pipe 14; allowing a steady flow of airfrom the pipe 'I3 to the pipe 'I4 and thence through the restrictions78, branch pipes Il, and valves 'I9 to atmosphere. The pressureeffective on the diaphragms 59 will remain constant, and the regulators23a will be in a balanced condition, holding the dampers I8 stationary.If the pressure in either of the chambers 2B should vary in theslightest degree for any reason, such as changes in the fuel bed, sootaccumulations in the boiler, variations in available draft, etc., thediaphragm 35 of the corresponding regulator 23a. will move and cause themotor 2l to make the proper adjustment in the position of the uptakedamper I8. If the steam pressure in the header I 5 should vary, thecontroller 6I will change the air pressure effective on the diaphragmG9, and the valve member 'II will take a new position, changing thepressure in the delivery pipe 14. This will alter the loading of theregulators 26a, throwing them temporarily out of balance, until thedampers I8 have moved sufliciently to vary the pressure in the chambers2i) and thus restore the regulators to a balanced condition. Anincreased steam pressure will cause the dampers i3 to move towardsclosed position, decreasing the flow of air for combustion, and viceversa. The load will be equally divided between the two boilers,regardless of variations which may occur in the ful beds, draft loss, ordraft distribution. By adjusting the valves 19, it is possible to varythe operating range of each of the regulators 23a, to t the conditionsencountered at the particular installation.

Having thus described my invention, what I claim as new and desire tosecure by Letters `VPatent is:

l. In combination with a fuel-burning furnace having a fuel bed, meansto maintain a sub-atmospheric pressure at the furnace outlet, a chamnber located immediately anterior to the fuel bed and provided with arestricted inlet opening through which air for combustion is drawndirectly from the atmosphere solely as a result of said sub-atmosphericpressure, a gas outlet damper at the furnace outlet, and a regulatorarranged to control the gas outlet damper in accordance with thepressure in the chamber, the regulator being adjustable so that thepressure differential across the said inlet opening may be varied tocontrol the rate of flow of the air for combustion in a desired mannerregardless of Variations in fuel bed resistance.

2. In combination with a fuel-burning furnace having a fuel bed, meansto maintain a sub-atmospheric pressure at the furnace outlet, a chamberlocated immediately anterior to the fuel bed and provided with arestricted inlet opening through which air for combustion is drawndirectly from the atmosphere solely as a result of said sub-atmosphericpressure, a gas outlet damper at the furnace outlet, an adjustableregulator arranged to control the gas outlet damper in accordance withthe pressure in the chamber, and automatic means to adjust the regulatorin accordance with the demand for heat, whereby the pressuredifferential across the said inlet opening will be varied and the flowof the air for combustion will be controlled in a desired mannerregardless of variations in fuel bed resistance.

3. In combination with a plurality of fuelburning furnaces, each furnacehaving a fuel bed, means to maintain a sub-atmospheric pressure at theoutlet of each furnace, a chamber located immediately anterior to eachfuel bed and provided with a restricted inlet opening through which airfor combustion is drawn directly from the atmosphere solely as a resultof said sub-atmospheric pressure, a gas outlet damper at the outlet ofeach furnace, an adjustable regulator for each gas Outlet damperarranged to control the same in accordance with the pressure in thecorresponding chamber, and automatic means to adjust all the regulatorsin accordance with the demand for heat from all the furnaces, wherebythe pressure differential across each inlet opening will be varied tocontrol the flow of the air for combustion in a desired mannerregardless of variations in fuel bed resistance.

JOHN J. KLINKER.

